Python Pandas : How can I count the number of times a value appears in a column based upon another column?

Question

This is my pandas dataframe I am referring to.

基本上我希望能够显示 'crime type' 的计数基于'council' 。例如，其中 'council == Fermanagh and omagh'数数 每个 'crime type' 都有不同的值这有道理吗？所以burgulary可能等于 1而，Anti-social behaviour'将是3另一个'council' ？然后我想将这些值绘制在条形图上。

希望这是有道理的。任何帮助都会很棒。谢谢。

Answer 1

我相信你需要groupby与 size :

df1 = df.groupby(['crime type', 'council']).size().reset_index(name='Count')

编辑:

df = pd.DataFrame({'crime type':['Anti-social behaviour','Anti-social behaviour',
                                 'Burglary','Burglary'],
                   'council':['Fermanagh and omagh','Belfast','Belfast','Belfast']})


df1 = df.groupby(['council', 'crime type']).size().unstack(fill_value=0)
print (df1)
crime type           Anti-social behaviour  Burglary
council                                             
Belfast                                  1         2
Fermanagh and omagh                      1         0

df1.plot.bar()